The present invention is related to the braking system for a battery operated floor conveyor, which features an electric steering control and an electric travel motor in addition. The individual functions of the floor conveyor are controlled by a vehicle control which is based on electronics.
In an electric steering control, a steering transmitter, a potentiometer or another angle transmitter for instance, generates a desired value signal, which is transmitted to an adjustment device for the steered wheel. In a steering regulation, the steering angle of the steered wheel is measured by a suitable sensor and transmitted to the controller, which moves the steering angle to the desired value in accordance with the comparison of desired and real value.
Of course, an electric steering control has to be monitored, so that there is no danger for the driver or the vehicle, respectively, at breakdown or the occurrence of errors. For these reasons, it is known to generate an error signal when such a condition occurs, which effects that an emergency stop or fail-safe brake is activated, which stops the vehicle down to standstill. Such a brake is usually an electromagnetically releasable spring brake. When the brake is energised, the brake discs are put out of engagement. When there is no more current, springs press the brake discs together and effect a corresponding braking.
It is also know to utilise such emergency stop brakes, which are usually arranged on the shaft of the travel motor, as a parking brake or for holding the vehicle on a slope. For instance, when the operation functions of the vehicle are switched off, such a brake is activated automatically. Furthermore, the operator can activate the emergency stop or fail-safe brake by generating a corresponding braking signal, when he/she wants to prevent the vehicle from self-acting movement in a slope situation.
In the known steering control, a relay which is arranged in the connection line between the vehicle battery and the emergency stop brake is opened instantaneously in the case of an error. Depending on the dimensioning of the springs of the brake, there will be a more or less strong deceleration. When the emergency stop brake is dimensioned such that it holds the vehicle even on steep slopes, the springs of the emergency stop brake must be dimensioned to be suitably stiff. This leads to a strong braking of the vehicle when the emergency stop brake is activated. The strong braking may result in a destabilisation of the vehicle, and through this, or even only through the strong deceleration, in an injury of the operator. Besides to the endangerment of the driver, the vehicle may also run out of the track when the wheel is blocking.
The present invention is based on the objective to provide a braking system for a floor conveyor which mitigates the effect of an emergency stop brake in the error case of the steering control.